Pine cones close in water because their scales absorb moisture and bend inward. As the scales dry, they can spread out again. You can watch this change with two open pine cones: put one in room-temperature water and leave the other dry for comparison.
For a November afternoon with grandchildren, this is a useful project to start before a board game or lunch. The checking takes only a few minutes at a time; reopening may carry on over several days. There is no need to sit beside the bowl waiting for movement.
The pine-cone experiment at a glance
| Part | Time to allow | What children do |
|---|---|---|
| Set up | 10 minutes | Compare two open cones and draw their outlines |
| Water checks | 2 minutes at 15, 30 and 60 minutes | Look for smaller gaps between scales |
| Drying checks | A few minutes daily | Compare the wet cone's outline as it dries |
| Review | 5 minutes | Describe what changed and what did not |
Suggested participants: children aged 6–12 with an adult managing the materials. These are activity-planning ages, not a product age rating. An adult can write down a younger child's spoken observations instead of asking for a full page.
Gather the materials before the visit
- Two mature, brown pine cones with open scales, preferably similar in size and from the same kind of tree
- One clear, wide bowl large enough for a cone
- One dry tray or plate for the comparison cone
- Room-temperature tap water
- A towel, pencil and notebook
- A clock or timer and two paper labels
Use untreated cones, not scented, painted, glittered or varnished decorations. Choose fallen cones from your own property or somewhere collecting is expressly allowed. Do not remove cones from a protected area or pick them from a tree for this activity.
An adult should inspect the cones and reject any with mould, sharp broken pieces or attached insects. Keep the materials out of mouths and away from food preparation. Wash hands after handling. Set the bowl on a stable surface away from electronics and empty it when the water stage is finished.
If the cones arrive damp and closed, let them air-dry first. Starting with visibly open scales gives you a clear beginning to compare against. Do not try to pry a closed cone apart.
Set up one wet cone and one dry cone
1. Give each cone a name
Put a paper label beside each position: “Water” and “Dry.” Keep the labels outside the bowl. Ask the child to choose one visible feature on each cone, such as a bent tip or unusually large scale, so you can recognise it later.
Look at both from the side. Are the gaps between the scales wide or narrow? Does one cone look rounder? Record those differences before adding water; two natural objects will not be identical.
2. Record a starting view
Draw a simple outline of each cone, then add three or four scales. A careful outline is more useful here than colouring every small detail. Write the start time beside the drawing.
For a more consistent comparison, put the notebook in the same position at each check and view the cone from the same side. A grandparent can take an optional starting photograph, keeping the camera away from the water.
3. Add water to just one cone
Place the “Water” cone in the bowl and add room-temperature water around it. Leave space below the rim. If it floats, record that rather than adding a weight. An adult can gently turn it occasionally so different sides contact the water; note that choice in the notebook.
Leave the “Dry” cone on its tray nearby. Keep both in the same room, away from a heater or strong direct sunlight. Do not add hot water, put the cones in an oven or change the temperature during this comparison.
4. Check the gaps, not just the colour
Return after about 15, 30 and 60 minutes. These are check-in times, not deadlines for a particular result. Ask: “Can you see the same gaps as before?” and “Which part looks different?”
A wet cone may look darker, but the main observation is the position of its scales. They may move closer to the cone's central axis, making the outline narrower. The dry cone provides something to compare with, rather than relying entirely on memory.
If there is little change after an hour, write that down. You can extend the observation while an adult remains responsible for the setup. Do not squeeze the cone to produce the expected shape.
Let it dry and look again
When you finish the water stage, an adult can lift the cone out, allow it to drain and place it on a dry tray. Empty the bowl. Record the time and draw the outline again.
Leave the cone to air-dry with space around it, away from direct heat. Check once a day and compare with the last drawing. Reopening may take several days; the cone and room conditions affect the timing. Do not promise a fully open cone before the grandchildren go home.
If the visit ends first, the adult can send a photograph of the same side the next day. Invite the child to say which detail to check next. That keeps the follow-up tied to their actual question rather than a general “Did you enjoy it?”
For an ongoing record, add the drawings to a simple nature journal. Keep this investigation together on one spread so the wet and dry stages are easy to compare.
Why can a cone move after falling from a tree?
The movement does not require the cone to be growing. Different tissues within a scale swell and shrink differently as they take up or lose water, causing the scale to bend. Researchers describe this as hygroscopic movement: movement associated with moisture.
Opening in dry conditions and closing in wet conditions is connected with seed dispersal. This does not mean your collected cone still contains seeds, or that every kind of cone will behave identically. For the underlying mechanism, see this published study of pine-cone scale movement.
A short explanation for a child is: “The material changes shape when it gets wet, and can change back as it dries.” Then return to the evidence on the table: which gaps changed, and when?
Keep the recording small and specific
Divide a page into three columns: time, water cone and dry cone. At each check, use one of three descriptions—open, partly closed or tightly closed—then add a detail if needed. These are your household's descriptions, not a scientific measurement scale.
A child who enjoys numbers can measure the cone's widest outline before wetting and after drying. Use the same orientation and do not press the scales against a ruler. Otherwise, a drawing is enough.
Try one spoken or written sentence: “At the start I could see gaps between these scales; later those gaps were smaller.” Separate that observation from the explanation about moisture. Our science writing prompts offer more ways to record a result without writing a long report.
An optional close-up before the water stage
The whole-cone change is visible without specialist equipment. If you already use a Peekorascope-Explorer™ Kids Digital Microscope, its built-in screen offers another way to examine a dry scale's surface before the experiment.
Keep the viewing tool at a separate, dry station, follow its instructions and age guidance, and record only the detail actually visible. Surface texture is different from seeing the internal mechanism; do not expect this activity to reveal the tissues responsible for bending.
Frequently asked questions
How long does a pine cone take to close in water?
There is no single time for every cone. Check during the first hour, then allow longer if necessary. Memorial University's Botanical Garden describes an open-and-close cone activity in which change can begin within an hour. Treat that as a guide, not a guaranteed result.
Why did our pine cone not close?
Check whether it was open initially and whether the scales contacted water. A coated decoration, damaged cone or a different type of cone may behave differently. Record what you used and try another untreated, open pine cone rather than changing several things at once.
Will the pine cone open again after drying?
An already-opened, responsive cone can reopen as it loses moisture. Air-dry it and check daily; allow several days rather than assuming it will reset overnight. Do not force the scales apart.
Is this experiment about hot versus cold water?
No. This version compares water exposure with staying dry. Both cones remain in the same room, and only room-temperature water is used. Comparing temperatures would be a different investigation with another variable to manage.
Before packing the notebook away, ask the child to choose one drawing to show someone else. Put the original prediction beside it—even if it was different from the result. The most interesting part of the page may be the detail neither of you expected to notice.
Featured image is an AI-generated editorial illustration of preparation materials, not a photograph of customer use or recorded experimental results.